This research will investigate the auditory capabilities of cochlear- impaired listeners who have residual acoustic hearing or usable electric hearing. In listeners with residual acoustic hearing, research will determine the extent to which auditory processing deficits are associated with magnitude of sensitivity loss, audiometric configuration, etiology, and performance on spectrally- and temporally-based speech tasks. Auditory capabilities to be investigated will include frequency resolution, frequency discrimination, temporal resolution, susceptibility to upward spread of masking, the ability to discriminate temporal envelopes of complex waveforms, and the existence and magnitude of intermodulation distortion. In listeners with usable electric hearing, research will investigate perceptual channel separation between electrodes, limits of place and periodicity coding, pitch perceptions associated with electrode location and stimulation rate, limits of intensity coding, loudness growth rates, and the ability to correctly perceive frequency and temporal cues of speech. In both types of listeners, knowledge about the auditory capabilities that remain will help determine better ways of encoding sound for the impaired auditory system.